Physicists measure exotic particle decay for first time, refining model of matter
Researchers analyzing 2.7 billion particle collisions have made the first precise measurement of how a rare type of matter decays, revealing new details about the fundamental forces at play. The findings could help validate theories that predict the behavior of particles used in future physics experiments and industrial applications.
Originaltitel: Helicity amplitude and branching fraction measurement of 𝜒<sub>𝑐𝐽</sub> → Λ¯Λ
<p>Utilizing 2712.4 ±14.3 million 𝜓(3686) events accumulated by the BESIII experiment, we perform a partial wave analysis of 𝜓(3686) → 𝛾𝜒𝑐𝐽 → 𝛾Λ¯Λ decay (𝐽 =0, 1, 2). The ratio of the helicity amplitudes with same (++) and opposite (+-) helicity for 𝜒𝑐2 → Λ¯Λ decay is determined for the first time to be 𝑅𝜒𝑐2 =0.575 ±0.048 ±0.018, with a relative phase angle ΔΦ𝜒𝑐2 =0.37 ±0.15 ±0.05 rad. The parameters of the angular distribution of 𝜒𝑐2 are determined to be 𝛼𝜒𝑐2 =−0.211 ±0.100 ±0.050 and 𝛽𝜒𝑐2 =−0.039 ±0.089 ±0.033, based on the distribution 𝑑𝑁/𝑑cos𝜃 =1 +𝛼𝜒𝑐2cos2𝜃 +𝛽𝜒𝑐2cos4𝜃. The width of 𝜒𝑐0 is determined to be 12.31 ±0.26 ±0.12 MeV. Additionally, the branching fractions for 𝜒𝑐𝐽 → Λ¯Λ are measured to be (3.662 ±0.048 ±0.111) ×10−4, (1.182 ±0.026 ±0.042) ×10−4, and (1.704 ±0.035 ±0.057) ×10−4 for 𝜒𝑐0, 𝜒𝑐1 and 𝜒𝑐2, respectively, where the first uncertainty is statistical and the second systematic.</p>